The work supported by this grant will continue to deal with the immunological & biological properties of the bovine leukemia virus (BLV), improvements in methods for detection of the virus in vivo and in vitro, and studies on the distribution and natural mode of transmission of BLV. The maintenance and characterization of our multiple case leukemia study herd will also continue. This herd is central to the rest of our current program and provides a unique animal population for future studies on the natural history of the disease. BIBLIOGRAPHIC REFERENCES: McDonald, H.C., Graves, D.C., Ferrer, J.F. Isolation and characterization of an antigen of the bovine C-type virus. Cancer Res., 36:1251-1257, 1976. Diglio, C.A., Ferrer, J.F. Induction of syncytia with bovine C-type virus. Cancer Res. 36:1056-1067, 1976.